Contactless wireless charging is an energy transfer method that electromagnetically transfers energy without wires, as opposed to the existing method that transmits energy through wires and uses it as a power source for electronics. Contactless wireless transmission methods include electromagnetic induction and resonant coupling. Electromagnetic induction is a power transfer method in which a power transmission part produces a magnetic field in a power transmitting coil (primary coil), and in which a receiving coil (secondary coil) is placed in a position where a current can be induced. Resonant coupling is the transmission of energy that uses resonance between a primary coil and a secondary coil, in which resonant mode energy is coupled between the coils as the primary coil and the secondary coil resonate at the same frequency.